Treatment of oils corrosive to copper



Patented June 14, 1949 TREATMENTOF"OILSCORBOSIVE'TU COPPER pprationnf Delaware NtiiDrawing-s Application "September 10, 1946;

SerialfiNo. 696,051;

acclaim. (Cl. 196-40 This invention V relates-etc; the: treatment of i petroleum hydrocarbons particularly; ofiitheewhite oil type which, during;their:preparationnhavee been .acid treated-toremove undesirable ponstltue ents such as .oIefina-aromaticsand the. like; and, more particularly, toacidetreated oilslwhichiaftert, neutralizatiom and. contacting ,iwitht or; percolar. tionv through clay; areefound. tor-be;- corrosive to. copper. This inventiondstalsoq concerned with the treatment of compositions-whichmaybepresdominantly petroleumdhydrocarbonzin character comprising mixtures-of acid-treated;hydrocar bons anclasimple or. pclymerizedi estentypfissofn; materials :which may be added .to improve .thec lubricating qualities of thespetrioleum .hydrocar,--- bons.

This inventionidesc-ribes" av process .ror, the treatment of 'I mineral oil, petroleumv products, and rprocessrlubricants whichsare corrosive toethe' copper strip as described .inrth'e Eederal- ..Standeard Stock CatalogVV-L-ZQI C, Isection.:IV, part 5, method.530.31.

Acid treatment ofrlvarious petroleumlhydroe carbons is a well"establishedi'artlandvariesrwitha the character ofthe particular hydrocarbon and #2 its eventual use. For example, low bbilinghydrm carbons from crackedstocksbbiling in-,-tl1'e. gasoe line range are treatedwith small 'percentagesioij sulfuric acid varying in concentration fromr95 98% for the purposeuof .removing ,andjpolymerize ing the more reactive olefinicrztypes .of materials and, after caustic washing,';,the 'materialis ,gene erally rerun and cut tospecificationboilingpoint; The purpose of this'treatment is 'to'remove the gum-forming constituents" of the gasoline and; improve the storage stability ofthe product. Desulfurization is generallyaccomplished at the same time.- Higher boilinguhydrocarbons, such as kerosene; may"be ligh'th' acid treated' with weak concentrations of sulfuric acid-* in order 'to' 40 improve burningqualityand odor or'may be highly acid treated-*with strong eacids varying from 100%" sulfuricacid'to: fiimi n'g- 'sulfliric acidr containing 20% by weighb of sulfur "trioxida Kerosene treated -with -strong-=-acids-*are used as ally require severeacid.treatmentiand'r during the process of their: refining: are subj'ecteda to the actionaof 5concentratedcsuinuricnacidivaryirig in strength from 98% to-zfuming siilfuricacidzzv De-v pending on the crude source; andhthe mature .xofa

the acid treatment used;thBSEFOilSWhEIIifiBiShBdEL 'Saybolt" color.

2;, may at times be corrosivezwvhenstested'Lwiththe; copperstrip tests One ofrthe obi ects-pf .this iinventionalis .toh-rene. den highly acidetreatedq'petroleum hydrocarbons. non-corrosive to copper.

Highly acidetreatedaoiliori white .oils' are .pree pared .by the. drastic. acId-fireatment"v with. sul; furici acid oia. hydrocarb'cn. di'stillate1v having a; viscosity in thecrange of-l301000lsecond.Saybblt at.f.100.' F. v Prior toitreatr'nent with' fumingosul. furicflacid,the oilmmay, tie-previously solventlexs, tracted, deasphalted,i.. dewaxed, ,ior. lightly, acid. treated to remove certain undesirable constitue ents. In treatingjjwith' the acid;v it is usual.- to apply the acid in a nu'mb'erioffi. dumps; during; which mechanicalorgair agitation-iis used'. Between successive dumps themixture is allowed toisettle .and the sludgedrawnoff and discarded. During the processpf acid treatment; a substantial quantity of 'oil"'solu'bl"e sulfonic acids .iknown as'-mahoganyacids are formed and" 'largelyore main dissolved irrthe oil. .Prior;to finishing the oil; these mahoganyacids must/"be 'removeol' either 1" bywasliing with Water orifnmiscil'ale= solvent'iinfl the acid state or theyjmay"'bepartiallypr" Wholly neutralized with a neutralizingagent such as the oxide; hydroxideand "carbonate of the alkali, and alkaline earth-metals; and or ammonium,"amines;* etc and eXtracted-withwater or dilute alcohol inthe form-of their salts comm'onlyknown' as mahogany soaps. The'pil after removal ofthe' acidic constituents and aitersteaming to remove any volatile solvent,- if present, but-before con= tacting w-ith'-'- or percolation through clay is" known as-a neutral oil." Dependingion the-'ini' tial 'character of the' oil, thesttengthof the acidused, the temperature of the aciwtreatmenti and" th tfital "quantity of-"acid appliedf the neutral oil wil l' -vary in color from-about a-10- to a +27 Tl'i'e*colored"material remaining inthe oilmay be hydrocarbon or resinousin na= ture or may consist def-" high" molecular weight sulfonates which are diffiiiulttdremove "by" or-'- clinary extraction. It' is the-"purpose of *contact"=- ing with or percolation through clay to-"remove"- thealast ;remaining coloredimaterial to yield a Water4white= oil having a"? S'aybolt colbr of" +30"? and-cup: Along with"color removali the oil is'ii'n proved: in taste'fandod'or and other quality'speci fications "such: as 'sus'ceptibilityz tc" oxidation "and" resistance Ito =formatio'n of rancidity when ex-"- posed:to-;ultra* violet? light? Very=often distillates and neutralofls' WiIIhave argoodcicopper test butpnf-processingi the meutral M- a poorrfcoppentst develops: In" a=* case of the distillate, the presence of small amounts of organic acids such as naphthenic acid act as passivatin materials for the surface of the copper and mask the true corrosive character of the oil. In the case of the neutral oils, the presence of small amounts of sulfonic acids or mahogany soaps act in a similar manner on the surface of the copper and give the appearance of a non-corrosive oil. Percolation of these neutral oils which removes the inhibitor then yields an oil which is corrosive to copper.

While a number of methods for the correction of bad copper tests have been described, such as the treatment of the oil with metallo-organic compounds, stron caustic, such as alcoholic potassium hydroxide, calcium hydroxide, and the like, these materials have the disadvantage of often causing the oil to go off color and off test in the medicinal grades and cannot be used when the oil is compounded with materials which will react with strong alkalis.

Another object of this invention is to treat an acid-treated petroleum hydrocarbon either in its neutral state or finished state (that is, after treatment with clay) so as to improve the corrosion test when tested with copper. I have now found that a satisfactory degree of improvement may be obtained by heating and mixing these neutral oils, which are corrosive to the copper test, with solutions of normal alkali metal sulfites, particularly sodium sulfite. The alkali metal sulfite is used in an aqueous solution which may vary in strength between 2 and 18 weight percent and is applied to the oil in a volume from to The choice of concentration is best determined by the nature of the oil, for example; its density, viscosity and tendency to form emulsions. The time necessary to complete the reaction is considerably shortened by the use of increased temperature. I have found that a temperature of from about C. to above about 100 C. is adequate, however, a temperature of 80 C. appears most practical. If, however, more rapid separation is required, higher temperatures may be used. In certain instances, it may be desirable to work at superatmospheric pressures, for example, in treating the lower boiling acid-treated material, it may be desirable to use superatmospheric pressures to keep the reactants in the liquid phase. Mechanical agitation, for example, by turbo-mixers, can be used or the oil may be treated in a tank in which a pump picks up the aqueous solution of sulfite, passes it through a heat exchanger to increase the temperature of the solution and brings it into a mixer to accomplish intimate contact of the two phases.

The length of contact between the oil and aqueous sulfite solution depends on the degree of corrosiveness present. For the usual amount of corrosion encountered, the time will vary from 20 minutes to 4 hours depending on the temperature used and the efiectiveness of mixer and the concentration of the sulfite. They are all variables best determined by test.

I have found that any emulsions formed by this treatment break readily on standing and the treated oil may be readily separated by known methods. After separation of the treated oil from the sulfite, the oil may be finished where required by contacting with or percolation through clay or, in the case of technical oils where the degree of refinement required is not as severe-as for the medicinal grades of oil, may be brightened by blotter pressing through a filter press. Neutral oils treated in this manner exhibit no corrosive action on copper, either in the neutral state or in the finished state after percolation through clay.

While I have disclosed treatment with sulfite on the neutral oil, the same treatment may be used on a finished oil where it is found the finished oil is corrosive to copper. When used on a finished oil, the oil may be further finished after treatment with the sulfite by filter pressing or by repercolation through clay.

In those cases where the corrosion on copper is unusually severe, it has been possible to dissolve the black coating obtained on the surface of the copper with acid and demonstrate that the black coating is predominantly copper sulfide. Experimental evidence has shown that the pure organic sulfides such as the dialkyl sulfides, diaryl sulfide and alkyl aryl sulfides may be added to a non-corrosive oil in a small amount without corrosiveness being imparted to that oil. However, when elemental sulfur in concentrations as low as one part per million is added to the oil or where a compound containing sulfur in a labile form such as a polysulfide linkage is added to the oil, corrosion will be exhibited in the oil due to the tendency of the labile sulfur or elemental sulfur to react under the catalytic influence of the copper and form hydrogen sulfide and other corrosive sulfur compounds. I have now found that the use of alkali metal sulfites under the conditions disclosed above is particularly effective in decomposing and removing all types of sulfur when present in either a free or labile form. While no limitation is to be had to the theory of reaction, it is believed that the mechanism of treatment involves production of elemental sulfur during the course of treatment which reacts with the alkali metal sulfite to form a non-corrosive thiosulfate which remains in the aqueous solution.

The copper strip test mentioned above consists in polishing a strip of thin copper sheet measuring in.x3 in. with a fine abrasive, immersing a copper strip in the oil to be tested and heating 3 hours in a steam bath at a temperature of 212 F. The results are rated numerically as follows: (1) shows no change in appear ance of the original copper strip; (2) shows a slight discernible yellow color but is still passable; (3) which does not pass (D. N. B), shows a pronounced bronze coloration; (4) shows a deep bronze to red color; (5) blue-black. In severely corrosive oils the copper may have a peacock hue changing to a brassy or silvery appearance. These silvery corrosive oils are rated number 6 to 10.

I have found that because of the substantial neutral character of the reagent used, my treatment can be used with oily compositions containing phenolic inhibitors, oil-soluble dyes and esters, all of which are unaffected by the treatment. My treatment produces improved quality tests. For example, taste and odor are improved, ability to resist deterioration by sunlight is improved, susceptibility of the oil to oxidation is decreased, the physical properties of the oil re main unchanged and, of course, corrosion to copper is substantially decreased.

All types of oils may be treated by my method particularly paraffinic and naphthenlc type oils. I have found that normal alkali metal sulfites, for example, ammonium sulfite, potassium sulfite, and sodium sulfite, preferably in aqueous solution, are all effective reagents for my disclosed treatment, however, sodium sulfite is the cheapest and is readily available commercially. Alkaline earth metal sulfites can also be used but they are insoluble in water and can be used in a dry state or in aqueous suspension.

If the oil, before sulfite treatment, is found to be acidic in nature or if the oil develops acidity during sulfite treatment, it is advisable to add alkali in the form of hydroxide or carbonate to counteract the acidity of the oil, that is, to make it neutral before sulfite treating.

With regard to the prior art, it is recognized that alkali sulfites have been used for the treatment of acid-treated oils, for example, U. S. Patent 2,257,914 to Sylvan R. Merley, describes a process for neutralizing a sulfuric acid-treated oil with aqueous solutions of alkali metal sulfites. It is noted in Merleys disclosure that alkali metal sulfite solution is used as the neutralizing agent in place of the customary hydroxide or carbonate. Merleys method is inapplicable and not feasible for the uses contemplated in this invention in that at no time, is the sulfite used for the neutralization of any acidity. My use of the sulfite is restricted to those oils which are perfectly neutral in character or which purposely contain a slight excess alkalinity in order to fix any hydrogen sulfide formed during process of treatment. Furthermore, any sulfonate formed during acid treatment is removed by washing with water or dilute alcoholic caustic treatment before applying sulfite treatment. Mcrley treats acid-treated naphthas which contain only a small amount of acid readily removable by water washing and which contain only traces of sulfonic acids so low in molecular weight as to be readily water-soluble without the formation of bad emulsions. On the other hand, the oils which I treat with sulfite have been treated with fuming sulfuric acid. In their acid state, therefore, they contain high concentrations of acid and high concentrations of sulfonic acids in comparison with those present in Merleys treatment. The neutralization with aqueous alkali sulfites of my highly acidic oils would produce severe emulsions which would not break without the use of additional materials such as alcohol which would be undesirable since the solubility of sulfite in dilute alcohol becomes quite low, and in order to accomplish complete neutralization of the acidity, it would require enormous amounts of alcoholic sulfite.

The effectiveness of my invention will be more clearly illustrated by the following examples:

Example 1 A parafiinic base oil having a viscosity of about 52 seconds Universal Saybolt at 100 F. which had been treated to produce a, white oil with fuming sulfuric acid, the sludge separated, the acid oil neutralized with sodium carbonate, alcohol washed to remove sulfonic bodies, and steamed to remove the alcohol, was found to be highly corrosive to copper.

The above acid-treated oil was refluxed in its neutral state at boiling temperature and atmospheric pressure with 20% by volume of a by weight solution of sodium sulfite for 1 hour. The layers were allowed to separate and the oil finished by clay percolation. The original oil, without any treatment with sulfite and after percolation through the same type of clay, showed a highly corrosive copper strip rated as a #9, while after treatment with sodium sulfite, a strip was obtained and rated as #1.

Example '2 A compounded hydraulic oil comprising a mixture of a 32 Saybolt viscosity oil and a 60 viscosity oil, both of which had been acid treated, containing in solution an acryloid polymer, a phenolic inhibitor, and an oil-soluble dye, showed a bad copper strip test and failed to pass the 168 hr. corrosion specification for such a mixture as specified in Federal Specification AN VVO- 366-3. Treatment of this oil mixture With 20% by volume of a 10% by weight solution of sodium sulfite at 70 C. for a period of 2 hours gave a product which when finished by filtration through a filter press, had a satisfactory copper test and satisfactorily'passed the above-identified corrosion specification, with no adverse efiect on any of the other physical tests.

Example 3 A Mid-Continent base white oil having a viscosity of seconds Saybolt at F. which had 'been produced by conventional acid treatment, separation of the sludge, neutralization of the acidity with sodium carbonate, extraction of the sulfonic bodies with dilute isopropyl alcohol,

steamed to remove the alcohol and finished by percolation through clay to produce a finished white oil was found on inspection to be off odor and taste and showed a poor response to the copper corrosion test. This oil was treated with 20% by volume of a 15% solution of sodium sulfite using mechanical agitation at a temperature of 80 C. for a period of 2 hours. The lower sulfite layer was removed, the clear bright oil layer finished by blotter-pressing through a plate and frame filter press. The oil finished in this manner showed good odor and taste and gave a good copper corrosion test. Repercolation of a portion of this oil through an additional quantity of clay yielded a satisfactory oil with respect to quality tests and copper corrosion. The untreated oil, when treated with an equivalent quantity of water for the same period of time and temperature showed no improvement either with or without additional clay percolation.

Example 4 A synthetic lubricant consisting predominantly of di-2-ethyl hexyl sebacate was found on inspection to possess a poor copper test. Materials of this type are normally not corrosive to copper but are subject to contamination with materials which may be corrosive to copper and in this instance, the origin of the corrosive material appeared to be one of contamination. The usual method of treatment such as redistillation under high vacuum and "blowing with inert gas failed to yield any improvement. Treatment of this ester with 10% by volume of a 5% solution of sodium sulfite at reflux temperature for a period of one hour followed by simple paper filtration in order to finish the ester gave a satisfactory corrosion-free product, which met specifications as to pour, free acidity, and so forth.

Numerous modifications may be made in the process by those skilled in the art without departing from the scope of the invention described.

What is claimed is:

1. A process for preparing petroleum hydrocarbon oil non-corrosive to copper, said oil having been treated with strong sulfuric acid, the sludge having been removed, the acid treated oil having been neutralized with a neutralizing agent, the product of neutralization having been extracted with an immiscible solvent, and the residual immiscible solvent having been removed from the oil, and the resulting oil. having been treated with clay, which comprises treating the said oil with an aqueous solution of a normal alkali metalsulfite.

2. A process for preparing Petroleum hydrocarbon oil non-corrosive to copper; said hydrocarbon oil having been treated with strong; sulfuric acid, the sludge having been removed; the acid havingbeen neutralized with a neutralizing agent, the product of neutralization having been extracted with an immiscible solvent, the residual immiscible solvent having been removed from the oil; and the resulting oil treated with clay, which comprises treatingthe finished oil with an aqueous solution of a. normal alkali metal sulfite at a temperature ofvfrom 40 C. to about 00 C.

for a period of time from about 20 minutes to 4 20 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,028,998.- Schulze et aL Jan. 28, 1936' 2,257,914. Merley Oct; 7, 1941 2,278,498 Shoemaker Apr. 7, 1942" 2,303,077 GiraitislB) "Nov; 24, 1942v 2,321,290 Giraitis (A) June 8,1943 

